The present invention relates to method and apparatus for uniformly distributing fibrous glass wool upon a collecting surface. In the manufacture of fibrous wool mats, particularly those used for building insulation, a heat softenable material such as molten glass is supplied to a centrifuging means wherein centrifugal forces cause streams of the molten heat softenable material to emanate from a multiplicity of holes located about the periphery of the centrifuge. These molten streams are then acted upon by an attenuating means located about the periphery of the centrifuge means. Said attenuating means may be a combustion burner, a high velocity blower, or a combination thereof. The molten streams of glass are thus attenuated into fine fibers that can be collected into a mass having a woolly texture.
In addition to attenuating the molten streams into wool fibers, the attenuating means further causes the formation of a cylindrically shaped flow of high velocity gases flowing axially away from the centrifuging means and toward a collecting surface. Entrained within said gaseous veil are the attenuated fibers. Hence, the gaseous veil becomes a conveyance means for distributing the attenuated fibers upon a suitable collecting surface.
Generally the collecting surface upon which the fibrous wool is collected is a moving belt having a surface dimension over which the wool must be distributed greater than that of the cylindrical veil emanating from the fiberizing device. Therefore, it becomes necessary to manipulate the veil to uniformly distribute the entrained fibers over the desired collecting surface dimension.
Many techniques are employed in the prior art to uniformally distribute the fibers over the collecting surface for example: U.S. Pat. No. 3,020,585 issued to Berthon et al. teaches the use of gaseous jets to collapse or flatten the cylindrical veil thereby distributing the entrained fibers over the collecting surface dimension transverse to the surface movement. The major disadvantage of this technique is that it does not permit control of weight distribution over the collecting surface upon which the fibrous wool is distributed.
U.S. Pat. No. 3,295,943 issued to Mabru, teaches that by unsymmetrically varying the ambient pressure surrounding the veil, the veil may be flattened and caused to oscillate transversely across the collecting surface. The ambient pressure is varied by use of a non-attenuating annular blower located about the attenuating means, or by controlling the induced air flow about the veil with movable baffles located about the fiberizing means. The major disadvantage of Mabru's teaching is that as the veil sweeps from one side of the collecting surface to the other, the veil geometrically changes from a flat configuration, with its major dimension parallel to the direction of collecting surface movement, to a cylindrical configuration as it sweeps across the center zone, returning to a flattened configuration as it reaches the opposite side of the collecting surface. Hence, without complex mechanical linkage means, and a highly sophisticated timing mechanism, uniformity of the resulting fiber pack is difficult to control.
U.S. Pat. No. 2,863,493 issued to Snow et al. on the other hand, directs alternating opposed jets of air or steam into impinging engagement with the veil, thereby collapsing the veil and oscillating it transversly across the collecting surface. While Snow produces a uniform distribution of fibers over the collecting surface there is a tendency for lamination and roping of fibers within the pack thereby affecting the structural integrity and thermal efficiency of the product.